Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-09-24
2004-09-21
Sellers, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C525S507000, C528S092000, C528S097000, C528S107000
Reexamination Certificate
active
06794478
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for preparing an epoxy resin, which uses a recovered epihalohydrin as a raw material.
2. Description of Related Art
Epoxy resins have been used in various fields of adhesives, paints, laminates, molding materials, and casting materials, including semiconductor sealing materials, because a cured article having excellent mechanical properties, water resistance, chemical resistance, heat resistance, and electrical properties may be obtained by curing using various curing agents.
The epoxy resin is industrially manufactured by a reaction between a phenol compound and an excess amount of epihalohydrin. In the industrial process for manufacturing the epoxy resin, there is generally used a manufacturing system of synthesizing the epoxy resin, recovering epihalohydrin remaining as the unreacted component in the system while distilling, and reusing the recovered epihalohydrin in the following manufacturing batch.
The recovered component mainly containing the epihalohydrin is usually contaminated with glycidol produced by the reaction between the epihalohydrin and an alkali. The glycidol contained in the recovered epihalohydrin decreases the concentration of epoxy groups in the resulting epoxy resin and also reduces electrical characteristics in the field of the semiconductor sealing material. Furthermore, the curing rate during the curing reaction is drastically reduced with the decrease of the concentration of the epoxy group.
Japanese Unexamined Patent Application, First Publication No. 2000-72845 discloses a process of distilling a crude reaction product of a raw phenol compound and epihalohydrin to obtain a first recovered solution containing epihalohydrin, distilling the residue again to secondly recover a fraction containing epihalohydrin, rectifying the second recovered fraction to recover epihalohydrin, mixing this epihalohydrin with the first recovered solution to obtain a recovered epihalohydrin having a low glycidol content, and synthesizing an epoxy resin using the epihalohydrin as a raw material.
As described in Japanese Unexamined Patent Application, First Publication No. 2000-72845, the process of recovering epihalohydrin only by distillation requires a considerable energy cost to reduce the amount of glycidol in the recovered fraction. The process is inferior in industrial-scale productivity because it requires a multi-stage distillation operation, and it is also inferior in reuse efficiency of epihalohydrin because gelation is inevitably caused by the thermopolymerization of epihalohydrin and glycidol contained in the recovered fraction in the rectification step of the recovered fraction and epihalohydrin always remains as a residue in the rectification step of the second recovered fraction.
BRIEF SUMMARY OF THE INVENTION
Therefore, an object of the present invention to be achieved by the present invention is to reduce the energy cost and to remarkably improve the reuse efficiency of epihalohydrin and the industrial productivity in the process for preparing an epoxy resin, which uses a recovered epihalohydrin containing a small amount of glycidol.
The present inventors have intensively researched to achieve the above object and have found that it becomes possible to industrially manufacture an epoxy resin from a recovered epihalohydrin using a simple apparatus without causing any epihalohydrin loss by recovering a first recovered fraction having a low by-product glycidyl content while continuously distilling a distilled fraction from the crude reaction product after the completion of the reaction, recovering a second recovered fraction having a low water-soluble organic solvent content, washing the second recovered fraction with water to obtain a purified fraction, and using the purified fraction as a raw material for synthesis of the epoxy resin, together with the first recovered fraction in the process for preparing an epoxy resin by reacting a polyhydric phenol compound with epihalohydrin in a water-soluble organic solvent in the presence of an alkali reactive catalyst. Thus, the present invention has been completed.
The present invention provides a process for preparing an epoxy resin by reacting a polyhydric phenol compound with epihalohydrin in a water-soluble organic solvent in the presence of an alkali reactive catalyst, which comprises the steps of:
(1) continuously distilling a distilled component from a crude reaction product obtained by the reaction to recover a first recovered fraction containing the water-soluble organic solvent, an unreacted epihalohydrin, and a by-product glycidol in an amount of 0.01 parts by weight or less based on 1 part by weight of the unreacted epihalohydrin;
(2) continuously distilling a distilled component to recover a second recovered fraction containing the by-product glycidol, the unreacted epihalohydrin, and the water-soluble organic solvent in an amount of 0.1 parts by weight or less based on 1 part by weight of the unreacted epihalohydrin;
(3) recovering the epihalohydrin by washing the second recovered fraction with water to remove the water-soluble organic solvent and the by-product glycidol from the second recovered fraction; and
(4) reusing the first recovered fraction and the recovered epihalohydrin as a raw material of the reaction.
According to the present invention, it is made possible to reduce the energy cost and to remarkably improve the reuse efficiency of epihalohydrin and the industrial productivity in the process for preparing an epoxy resin, which uses a recovered epihalohydrin having a low glycidol content.
DETAILED DESCRIPTION OF THE INVENTION
Examples of the polyhydric phenol compound used in the process of the present invention include ortho-cresol novolak resin, phenol novolak resin, brominated phenol novolak resin, alkylphenol novolak resin, polycondensate of phenols and hydroxybenzaldehyde, naphthol novolak resin, polyadduct of phenols and dicyclopentadiene, bisphenol A, bisphenol F, tetrabromobisphenol A, biphenol, tetramethylbiphenol, binaphthol and dihydroxynaphthalene. Among these compounds, cresol novolak, binaphthol, dihydroxynaphthalene, or a polyadduct of phenols and dicyclopentadiene is preferred because an epoxy resin thereof having excellent heat resistance, water resistance and soldering cracking resistance is obtained in purposes such as semiconductor sealing materials.
Examples of epihalohydrin to be reacted with the polyhydric alcohol include epichlorohydrin and epibromohydrin. Among these compounds, epichlorohydrin is preferred in view of the availability. The process of the present invention uses virgin epihalohydrin as the entire epihalohydrin to be charged in a first batch for manufacturing an epoxy resin, but uses epihalohydrin recovered from the crude reaction product in combination with virgin epihalohydrin corresponding to epihalohydrin to be consumed during the reaction and epihalohydrin to be lost during the purification, in batches which follow the first batch.
The reaction between the polyhydric alcohol and epichlorohydrin is carried out in the presence of a water-soluble organic solvent. The reaction rate during the synthesis of the epoxy resin can be enhanced by using the water-soluble organic solvent. Examples of the water-soluble organic solvent include ketones such as acetone and methyl ethyl ketone; alcohols such as methanol, ethanol, 1-propyl alcohol, isopropyl alcohol, 1-butanol, secondary butanol and tertiary butanol; cellosolves such as methylcellosolve and ethylcellosolve; ethers such as tetrahydrofuran, 1,4-dioxane, 1,3-dioxane and diethoxyethane; and aprotic polar solvents such as acetonitrile, dimethyl sulfoxide and dimethylformamide. These water-soluble organic solvents may be used alone, or two or more kinds of them may be used in combination to adjust the polarity.
Among these solvents, a water-soluble organic solvent having a boiling point at normal pressure (0.101 MPa) of 120° C. or less is particularly preferred because the residual amount in the second reco
Arita Kazuo
Ogura Ichiro
Armstrong Kratz Quintos Hanson & Brooks, LLP
Dainippon Ink and Chemicals Inc.
Sellers Robert
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